Coil springs are tied down firmly across their tops to prevent them from slipping sideways out of position. They should be tied to uniform height so that each spring's upward expansion is controlled. Before tying, springs usually stand about 1 1/2 in. (3.5cm) above the "normal" height. Firm springs are often tied at freestanding height (1 1/2 in. above normal height). Medium springs are generally tied 1 in. (2.5cm) below normal height and soft springs 2 in. below normal height.
Springs lose resiliency when compressed by tying. Extra height above the frame increases the resiliency of the springs. In seats, tops of springs, after tying, should be a minimum 3 in. (7.5cm) above the frame. This permits them to be depressed without taking up all slack in the spring twine.
Seat springs may be tied to form round or flat tops according to need or preference. Single sets of springs used without cushions are usually tied with a round contour for appearance and comfort. Flat-shaped tops are used particularly when two sets of springs or a removable cushion is used. For flat seats, return tie is fastened to the third coil from the top.